1. Field of the Invention
This invention relates to torches. More particularly, it relates to cutting torches having a plurality of tubes therewithin. In a particular aspect it relates to an improvement in cutting torches employing the injector type mixer.
2. Description of the Prior Art
The advent of welding solved many problems that had plagued manufacturers earlier. The use of torches, such as cutting torches, welding torches, heating torches and the like, also helped the repairman perform a variety of repairs on the site instead of having to return an article to the factory to be repaired. There have been employed in the prior art a wide variety of types of torches. One of the types is known as the injector type mixer in which one of the gases being flowed down a pre-heat tube is emitted in a high speed stream to aspirate the other gas into admixture therewith. In theory, the injector type mixers have offered more flexibility than any other type of mixer. In actual use, however, the injector type mixers have always had one major drawback, that being a tendency to have sustained burning on flashback, to burn up the torch when used with certain fuel gases, such as acetylene. Injector designers in the past have tried to get around this by limiting their use to only fuel gases that are difficult to make flashback or by restricting the pressure and orifice sizes, or tip sizes that can be employed.
The closest prior art of which I am aware is U.S. Pat. No. 2,198,342; although there are other patents extending back to U.S. Pat. No. 1,262,351, April, 1918, that show the use of mixing spirals. The patent U.S. Pat. No. 1,276,893, shows the intricate passageways to prevent backfiring of a torch. U.S. Pat. No. 2,263,655 shows a pipe coupling having a spiral fin 20. In the closest are U.S. Pat No. 2,198,342, the use of a mixer and an aspirating jet of oxygen is shown. Experience with that torch indicated, however, that sustained burning could be experienced on flashback unless the respective mixers and mixer orifices were changed out with different gases. Expressed otherwise, the blow pipe of U.S. Pat. No. 2,198,342 could be employed with certain gases, such as natural gas and the like that were normally resistant to flashback and sustained burning anyway; but could not be employed for acetylene, or other difficultly employed gases without changing out the mixer and the mixer orifice--an undesirable procedure.
Thus, in the prior art, the use of injector mixer type torches have required changing out the mixers and the mixer orifices for each of the fuels being employed or risk sustained burning on flashback so as to damage the torch.